Device for programming the afterburning-initiation phase in a turbojet engine

ABSTRACT

In and for a turbojet engine of the kind comprising a compressor, an afterburning duct, means for supplying the afterburning duct with fuel and means for metering the flow of fuel injected into the duct, the flow-metering means being sensitive to a parameter Beta P2, in which P2 is a characteristic working pressure of the compressor and Beta is a coefficient which is less than or equal to one, a programming device for the afterburning-initiation phase, which device comprises means for modifying the coefficient Beta to reduce temporarily the coefficient Beta during the afterburninginitiation phase, and means for automatically bringing the Beta -modifying means out of action after the moment at which the fuel has actually been ignited in the afterburning duct.

States atent 1 Galmiche et a1.

DEVICE FOR PROGRAMMING THE AFTERBURNING-INITIATION PHASE IN A TURBOJETENGINE Inventors: Pierre Michel Andre Galmiche, Le

Mee-sur-Seine; Henri Jacques Jourdier, Moissy-Cramayel; Pierre PaulLouis Odeyer, Paris, all of France Societe Nationale dEtude et deConstruction de Moteurs dAviation, Paris, France Filed: Feb. 16, 1973Appl. No.: 333,371

Assignee:

Foreign Application Priority Data Feb. 18, 1972 France 72.05566 US. Cl60/243; 60/241; 60/3928 R Int. Cl. F02k 3/10 Field of Search 60/241,239, 261, 233,

References Cited UNITED STATES PATENTS 6/1965 Herbert 60/239 3,271,9469/1966 Desmazes 3,298,180 l/1967 Trinkler 60/239 X 3,714,784 2/1973Glaze 60/243 3,719,047 3/1973 Briotet 60/239 FOREIGN PATENTS ORAPPLICATIONS 796,203 6/1958 United Kingdom 60/243 PrimaryExaminer-C1arence R. Gordon Attorney, Agent, or Firm-William .1. Daniel[57] ABSTRACT In and for a turbojet engine of the kind comprising acompressor, an afterburning duct, means for supplying the afterburningduct with fuel and means for metering the flow of fuel injected into theduct, the flowmetering means being sensitive to a parameter BP in whichP is a characteristic working pressure of the compressor and B is acoefficient which is less than or equal to one, a programming device forthe afterburning-initiation phase, which device comprises means formodifying the coefficient B to reduce temporarily the coefficient Bduring'the afterburning-initiation phase, and means for automaticallybringing the B-modifying means out of action after the moment at whichthe fuel has actually been ignited in the afterburning duct.

16 Claims, 9 Drawing Figures PATENTED HAY I 31975 Angle of lever o( and72-.- 720% Engagement of afterourn/ng (67) Afterburning feed de vice(78. 73

Afterburn/n igniting de vi c QQZS Ignition de iECtiO/I Flow of afterburn/ng fuel.

thro tt/ed. do an after:

burning in operation out of operation 0 eration P t j in operation outof operation :out of operation lit extinguished extinguished I litextinguished fu/ /oad after urn/ng zero /thrott/ed down afterburn/ngtime (seconds) mmgn MAY] 3 m5 Angle of lever ix Afterpurning rese/ec;t/on device (7 0) X X ref.

Y: Yref.

Locking (102) Afterburning feed device (78- 79) ffi-modifierj Signal.lampe for after.

burn ing ignition de vlceKiS? Signal lamp for actual funct oning ofaftcr purn/ng(52) Flow of af terburnin g fu e/ SHEET 7 0i 7 fu/L loadafterburning DRY' locked out of ope ation in operation out of operationout of opera ion V 7 s in oat/0n out of act/on lit extinguishedextinguished lit ext/ngui'shed fu// /oad restrained afterburn/ng flowzero time (seconds) DEVICE FOR PROGRAMMING THE AFTERBURNING-INITIATIONPHASE IN A TURBOJET ENGINE This invention relates to a device forprogramming the afterburning-initiation phase in a turbojet engine whichis intended to propel a flying vehicle such as an aircraft, the turbojetengine comprising, in particular, a compressor, an afterburning duct, adevice for supplying the afterburning duct with fuel, and a device formetering the flow of fuel injected into the duct, the flow-meteringdevice being sensitive to a parameter ,BP in which P is a characteristicworking pressure of the compressor, and ,8 is a coefficient which islower than, or at the most equal to, one.

As is already known, a turbojet engine having afterburning comprises thefollowing elements, arranged one after the other in the direction inwhich the gas flow passes through; a compressor, a main combustionchamber, an expansion turbine, an afterburning duct, and a propulsionnozzle.

A supply device, which can be brought into, or out of, operation, makesit possible to direct a flow of afterburning fuel towards theafterburning duct when extra thrust is required. This flow is usuallyregulated with the aid of a regulator/metering device which isassociated with an engine control lever operated by the pilot. Anignition device, which can be brought into, or out of, operation, isgenerally provided in order to facilitate the initiation of combustionof the fuel which discharges into the afterburning duct.

The initiation of afterburning is only allowed under certaincircumstances which, in the case of aircraft equipped with turbojetengines having afterburning of the known type, represent many restraintsor instructions for the pilot.

Thus, the pilot must see to it that, at the moment at which he tilts theengine-control lever to the AFTER- BURNlNG position, the speed ofrotation of the compressor and the temperature of the gases are equal totheir respective fullload values under dry operating conditions, that isto say without afterburning. The use of afterburning is, in fact, onlynecessary and advanta geous when the rest of the engine is alreadyworking at full load. In addition, correct regulation of afterburningpresupposes that the abovementioned parameters are kept constantthroughout the period for which afterburning is in operation.

In order to prevent any premature initiation of afterburning (that is tosay, before the dry full load has really been reached), the pilot musttherefore have kept the engine control lever in the FULL-LOAD DRYposition for a sufficiently long time to enable the parameters toactually settle at their desired values. He therefore may not directlyswing the control lever from the THROTTLED-DOWN DRY position into anyposition whatsoever in the AFTERBURNING sector, without having markedtime for a period of stoppage at the FULL-LOAD DRY position, and havingmade sure that the conditions allowing the engagement of afterburningare really complied with.

As will be realised, this constitutes a particularly dis advantageousoperating restriction since it complicates the task of the pilotwithout, however, ruling out all risk of incorrect operation. It is,moreover, the basic cause of a loss of time during the accelerationprocess of an aircarft (for example on take-off or when climbing) whichis propelled by a turbojet engine of this kind. Nevertheless, it hashitherto seemed difficult, or even impossible, to escape this problem.

Another constraint concerns the starting-up of combustion in theafterburning duct. The ignition device used for this purpose is oftenconstituted by means which make it possible to inject into the maincombustion chamber, for a certain period, an additional quantity offuel, via an ignition injector the opening of which is located, forexample, slightly upstream of the turbine. The flame which results fromthis passes through the turbine and thus makes it possible to obtainignition of the fuel in the afterburning duct. This device, which hasthe advantage of being simple, nevertheless possesses the drawback thatit causes, when brought into operation, an additional rise in thetemperature of the turbine blades, which temperature, under dryoperating conditions (that is to say under normal operating conditions,without afterburning), is already very high in modern jet propulsionengines.

In order to reduce this additional temperature rise to a minimum, it istherefore expedient to limit, to the greatest possible extent, theperiod for which fuel is injected through the ignition injector.Consequently, this injection must not start too early (that is to saybefore the conditions permitting the engagement of afterburning havebeen fulfilled), or be extended too late (that is to say after ignitionof the fuel has actually been achieved in the afterburning duct) or fortoo long a time (in the event of unsuccessful igniting). The taking intoacount of these restraints therefore adds still further to thecomplexity of the pilots task.

The primary object of the present invention is to free the pilot fromall the instructions and restraints mentioned above, and to enable himto initiate afterburning without any special precaution having to beobserved.

A further object of the invention is to provide better protection forthe turbine, by the automatic monitoring of the start and finish ofinjection of the igniting fuel.

For this purpose, the invention provides a device for programming theafterburning-initiation phase, which comprises means for modifying thecoefficient B, which are designed to temporarily reduce the coefficientB during the afterburning-initiation phase, and means for automaticallybringing the ,8-modifying means out of action after the moment at whichignition of the fuel has actually been obtained in the afterburningduct.

These means for modifying the coefficient B thus constitute a device fortemporarily restraining the flow of afterburning fuel.

The action of this flow restraining device is such that, for the entireduration of the afterburning-initiation phase, the flow of fuel actuallyinjected into the afterburning duct remains very small (for example,equal to, or lower than, the flow corresponding to ThrottleddownAfterburning), and this remains true whatever the position displayed bythe engine control lever.

Starting, for example, from the THROTTLED- DOWN DRY position, the pilotcan therefore move the engine control lever in one go direct to anyposition in the AFTERBURNING sector including the FULL- LOADAFTERBURNING position in such a way as to preselect any load or rate ofafterburning whatsoever, without having to worry about marking time fora period of stoppage at the FULL-LOAD DRY or THROTTLED-DOWN AFTERBURNINGposition. In actual fact, everything takes place during the period inwhich the fi-modifying means is in action, as if the control lever werebeing held artificially in the ENGAGE MENT AFTERBURNING orTHROTTLED-DOWN -AFTERBURNING position. An awkward restraint and an idleperiod are thus eliminated.

According to one arrangement of the invention which is applicable to aturbojet engine equipped with an ignition-detecting device (for examplean ionization probe) which emits a signal at the moment at whichignition of the fuel has actually been obtained in the afterburningduct, the means for disabling the B-modifying means are controlled bythe ignition signal. A timing device may also be provided in order tointroduce a predetermined delay into the bringing out of action of theB-modifying means, after the moment at which the ignition signal hasbeen emitted. It is thus. possible to prolong the action of theB-modifying means slightly beyond the moment at which combustion hasactually been initiated in the after-burning duct, so as to enable suchcombustion to become stable.

According to one arrangement of the invention, the B-modifying meanscomprise a pressure-modifying reducer which is supplied with fluid at apressure of 3P The means for disabling the B-modifying means thencomprise means for rendering the pressure-modifying reducer inoperative.

According to an arrangement of the invention which can be applied to aturbojet engine of the kind in which the pressure parameter [3P isgenerated, starting from the pressure P in a pressure-reducing devicecomprising at least one main reducer, the pressure-modifying reducer isconstituted by an auxiliary reducer which is fed by the main reducer.

The pressure-modifying reducer may advantageously comprise a capacity orspace which is fed, through a constricted orifice, with fluid at apressure of 6P and communicates with a low-pressure space throughanother constricted orifice forming a leakage outlet through which,under operating conditions, the fluid escapes from the capacity at asonic speed. The means for disabling the pressure-modifying reducer may,in that case, comprise means for stopping the escape of the fluidthrough the leakage outlet, for example, by cutting off communicationbetween the capacity and the leakage outlet.

Another arrangement of the invention, which can be applied to a turbojetengine comprising, in addition, means (such as a valve) for bringinginto, or out of, operation the supply device for the afterburning fuel,comprises an afterburning-preselection device, which may occupy either adry operating position or an afterburning operation position, and alsomeans (comprising, for example, a locking device) which are sensitive toat least one working parameter of the DRY turbojet engine, such meansbeing designed to automatically activate the supply device when,'withthe preselection a single lever which is capable of successivelycovering a DRY sector andan AFTERBURNING sector), the aforesaidpreselection device. may advantageously be coupled to the control lever.

The pilotis thus freed from the duty of insuring that the speed ofrotation and the temperature of the gases have reached the thresholdpermitting engagementof afterburning, and he can now, without taking anyprecautions, swing the engine control lever from any position whatsoeverin the DRY sector into the AFTER- BURNING sector. By doing this, he is,in fact, exerting a double effect; on the one hand, he is calling uponthe engine to function (if it was not doing so already) at full-loadDRY, and, on the other hand, he is preselecting the functioning underafterburning conditions. But I this preselection does not, in turn, giverise to actual operation of the device for supplying the .afterburnin gfuel, until the above-mentioned parameter or parameters have reachedvalues which show that full-load DRY has actually been obtained. 7 I

According to a further arrangement of the invention, which is applicableto a turbojet engine equipped with a device for igniting the fuel whichdischarges into the V afterburning duct, which igniting device can bebrought into, or out of, operation, the means which are sensitive to theabove-mentioned parameter(s) are also adapted to automatically bringsuch igniting device into opera-f tion when, with the preselectiondevice in an afterburning operation position, the selected parameter orparameters have reached the threshold indicated previously.

Since activation of the igniting device and of the 'de-. 1 I

vice for supplying the afterburning fuel are controlled by the samesignal, it will therefore be seen that the ig nition process propercannot begin before the device for supplying afterburning fuel isactually. functioning. i

ming the afterburning-initiation phase, in accordance with theinvention, possesses the three-fold advantage that it considerablysimplifies the task of the pilot, provides better protection of theturbine, and leads to a major saving in the time required to establishafter? burning.

The invention will now be further described, by way of example, withreference to the accompanying draw-- ings, in which:

FIG. 1 is a diagrammatic view of a turbojet engine with afterburning,which may be equipped with a programming device according totheinvention;

FIG. 2 is a diagrammatic. view of part of a regulator/metering device,fitted to the turbojet engine illustrated in FIG. 1, for the flow ofafterburning fuel;

FIG. 3 is a chart illustrating the functioning of the regulator/meteringdevice shown in FIG. 2; A

FIG. 4 is a simplified functional diagram illustrating a knownafterburning-initiation sequence in a turbojet engine of the kindillustrated in FIG. I; FIG. 5 is a diagrammatic view of apressure-reducing device of known type, which works in conjunction withthe regulator/metering device shown in FIG. 2;

FIG. 6 is a diagrammatic view of a pressure-reducing device which issimilar to that shown in FIG. 5 but is modified in order to form part ofa device for programming the afterburning-initiation phase, according tothe invention;

FIG. 7 is a simplified functional diagram showing anafterburning-initiation sequence which is obtained by using aprogramming device according to the invention;

FIG. 8 is a combination of charts showing the development, as a functionof time, of various parameters or of the position of various members, inthe course of the known initiation sequence shown in FIG. 4; and

FIG. 9 is a combination of charts which is similar to that shown in FIG.8 but relates to the case of an afterburning-initiation sequence whichis obtained by using a programming device according to the invention.

In FIG. 1 there is illustrated a turbojet engine which is intended forthe high-speed propulsion of a vehicle, such as an aircraft. Thisturbojet engine comprises, after an air-intake (not shown), a compressor1, a main combustion chamber 2, an expansion turbine 3, an afterburningor re-heating duct 4, and a propulsion nozzle 5 the cross-sectional areaof which can be regulated by means of flaps 6. The arrows F symbolizesthe flow of hot gases escaping from the turbine.

Main injectors 7 open into the main combustion chamber 2. A pump 8,which is supplied, via induction piping 9, with fuel originating from asource which is not shown, impels the fuel towards the injectors 7through delivery pipes 10, 11 between which there is interposed a flowregulator/metering device 12 of conventional type.

Mounted in the afterburning duct 4 are manifolds R R R;,, which areintended to permit the injection, into the flow F of hot gases, of aflow C of afterburning fuel which is impelled by a pump 13 through pipesl4, 15, a purger/distributor 16 and pipes CR CR CR the flow beingmetered with the aid of an afterburning regulator/metering device 17.The pump 13 is supplied with fuel from a source, which is notillustrated, via a supply device comprising an induction pipe 18 whichcan be blocked by means of an inlet valve 19. The supply device 18/19 isin, or out of, operation according to whether the inlet valve 19 is openor closed.

The rotational speed (if necessary corrected to take account of theflight altitude) of the compressor 1, and a characteristic workingpressure, for example the delivery pressure of the compressor, have beendesignated by the reference symbols N and P respectively.

The pressure P which is taken off at a suitable point on the compressor1, is transmitted, via a pipe 20, to a pressure-reducing device R whichgenerates, from the pressure, a reduced-pressure parameter ,BP in which,8 is a coefficient which is at most equal to one. The reduced-pressureparameter BP is transmitted, via a pipe 22, to the regulator/meteringdevice for the flow of afterburning fuel.

The reference numeral 23 designates a control box which is connected, byfunctional connections 24, 25, to the two regulator/metering devices 12and 17 respectively, and from which there passes out an enginecontrollever M which is at the disposal of the pilot of the aircraft.This lever angularly covers a graduated sector, its position on thesector being defined by an angle a which is measured from a suitablestarting point. Corresponding to each angle a of the lever, there is agiven load which is set by the pilot. Five typical lever angles whichcorrespond to the following situations: THROTTLED-DOWN DRY (that is tosay without afterburning), FULL-LOAD DRY, ENGAGE- MENT AFTERBURNING,THROTTLED-DOWN AFTERBURNING and FULL-LOAD AFTERBURN- ING, have beendesignated by 01,, a a a and a, respectively. That portion of the sectorwhich is covered between zero and a constitutes the dry sector, whereasthat portion of the sector which is covered beyond 01 constitutes theafterburning sector. The engagement of afterburning is effectedautomatically when the lever M passes to the position defined by theangle a The turbojet is also equipped with a device for igniting thefuel which discharges into the afterburning duct. This deviceessentially comprises an auxiliary, or igniting, injector 26 which opensinto the main combustion chamber 2 of the jet engine and makes itpossible, when afterburning is being initiated, to deliver an extraquantity of fuel, upstream of the turbine 3, for a certain space oftime. This fuel ignites because of the high temperature prevailing inthe chamber 2 and thus produces a tongue of flame which passes throughthe bladings of the turbine 3 to ignite the afterburning fueldischarging, in particular, from the upstream injection distributor R1.

The igniting injector 26 is supplied, via a pipe 27 fitted with aone-way valve 28, with fuel which has been taken off at the outlet ofthe pump 13. An obturator 29, functioning on the all-or-nothingprinciple, makes it possible to bring the igniting device comprising theauxiliary injector 26 into, or out of, operation.

The afterburning duct is fitted with an ignitiondetecting device 30,which is adapted to emit a signal at the moment at which ignition of thefuel has actually been obtained in the afterburning duct. This signal,suitably amplified in an amplifying device 31, intervenes in theafterburning-initiation sequence, as will be explained later on. Theignition-detecting device may be of any known type, such as anionization probe, fibre-optics detector, pressure-variation detector,etc..

The temperatures of the gaseous flow which prevail immediately upstreamof the turbine 3, immediately downstream of the turbine, and in thenozzle 5, have been designated by T T and T respectively.

FIG. 2 shows, in greater detail, the regulator/metering device 17 forthe flow of afterburning fuel.

This regulator/metering device is sensitive, on the one hand, to theabove-mentioned reduced-pressure parameter BP and, on the other hand, tothe lever angle a in the AFTERBURNING sector. It comprises, inparticular, a rocking lever 40 which is articulated about a pin 41 andhas two lever arms, the ratio between which is designated by a/b. One ofthe ends 40a of the rocking lever controls, via a servo-jack 42, thedisplacement of a metering piston device 43 which works in conjunctionwith a metering slit 44. A regulating valve (not illustrated) makes itpossible, in known manner, to regulate the drop in pressure which takesplace through the metering slit 44. For a given drop in pressure,therefore, the flow C of afterburning fuel is solely a function of theexposed cross-sectional area of the metering slit, that is to say, ofthe position of the metering piston device 43.

The reduced pressure 3P which prevails in, or is taken off from, acapacity 45, controls the movements of the other end 40b of the rockinglever 40 via aneroid capsules 46 and a hydraulic amplifier 47. For agiven drop in pressure through the metering slit 44, therefore, theregulator/metering device 17 makes it possible to keep the ratio C/BPconstant and equal to the ratio a/b of the lever arms of the rockinglever 40.

This ratio can be changed by varying, with the aid of the regulatinglever M, the position of the articulation pin 41 in a slide 400 carriedby the rocking lever.

FIG. 3 is a chart which shows the functioning of the regulator/meteringdevice 17 in the C, [3P plane, for each lever angle a, and in particulara a (THROT- TLED'DOWN AFTERBURNING) and a a (FULL- LOAD AFTERBURNING).

The principle of this afterburning regulation is known per se. Becausethe use of afterburning is only necessary when the dry engine is alreadyworking at full load, the main regulator/metering device 12 keeps therotational speed N of the compressor and the temperature T upstream ofthe turbine (and therefore also the temperature T downstream of theturbine) constant throughout the period for which afterburning is inoperation.

The afterburning load may be characterised by the increase intemperature T -T,. Now, this increase in temperature is proportional tothe ratio C/D, in which C is the flow of afterburning fuel, and D theflow of air passing through the afterburning duct. This flow of air isitself proportional to a characteristic working pressure (for examplethe outlet pressure) P of the compressor, in view of the fact that thespeed of rotation N and the temperatures T and T are kept constant bythe main regulation. It will be deduced from this that the afterburningload is really represented by the ratio C/P In actual fact, theparameter P is often corrected by a coefficientfl lower than one (forexample, of the order of 0.87), which makes it possible to adjust, onthe bench, the maximum thrust of the turbojet engine under afterburningconditions, but which normally plays no part in the principle on whichafterburning regulation functions. The flow Cof afterburning fuel istherefore supplied by the expression C BP f(a).

From his control lever M, the pilot can thus select an afterburning loadby regulating the ratio C/BP while the main regulation system continuesto keep the parameters N, T and T constant, and the disturbances broughtabout by the functioning of afterburning downstream of the turbine arecompensated for by a more open position of the propulsion nozzle 5.

FIG. 5 shows, by way of an example, a pressurereducing device of knowntype (see, for example, French Pat. No. 1,376,588) which makes itpossible to produce, from the pressure P the reduced-pressure parameter3P This device R comprises a main pressure-reducer 21 which is made up,in particular, of a reduced-pressure capacity or space 50 of which thecapacity 45 constitutes an extensionvia the pipe 22. The capacity 50opens on to a space which is under low pressure (for example theatmosphere or, possibly, a space which is under subatmospheric pressure)through a constricted diaphragm 51 which is advantageously adjustable,and this capacity is connected, via a constricted orifice 52, with thepipe for taking-off the pressure P A blocking device, such as a valve 80which is controlled from the regulating lever M via a functionalconnection 81, makes it possible to feed the pressurereducer 21 onlywhen the lever M is in the afterburning sector (a 2 a Under thesecircumstances, an escape of air occurs through the constricted orificeSlat sonic speed and there is set up, in the capacity 50 (andconsequently in the capacity 45), a reduced pressure (3P in which B is aconstant coefficient of reduction which depends only upon the respectivecharacteristics of the constricted orifices 51 and 52. y

In order to permit an increase in richness in the afterburning ductunder high-altitude conditions, an additional overload circuit may alsobe provided. This cir cuit comprises, in particular, a pipe 53 which istappedi off from the pipe 20 and opens into the capacity 45 through aconstricted orifice 54. An electrically controlled valve 55 makes itpossible to shut off or open the pipe 53 according to whether thealtitude at which the aircraft is flying is lower or higher than acertain ceiling (for example, 30,000 feet). The valve 55 is controlledby a contactor 56actuated by an altitudedetector 57. The coefficient ,8thus passes from'a normal low-altitude value (for example ,8 0.87) to anormal high-altitude value (for example ,8 0.93).

It will be noted that, at rest, when the pressurereducer 21 is not beingfed (that is to say, when the control lever M is in the dry sector), thecoefficient B supplied .by the pressure-reducing device R. may be re-.

garded as being equal to one, because the capacity 50 is then at ambientpressure and there is no leakage through the constricted orifice 51. I

With reference to FIG. 4, there will now be described i The obturator 29for controlling the igniting device 26 is'an electrically controlledvalve which when at a rest, is in the blocking position. It will also benoted that the inlet valve 19 is of the hydraulic-control type and thatit opens under the effect of a pressurised control fluid (such aspressurised fuel taken off from the main fuel circuit, between the pump8 and the regulator/metering device 12) which is carried in a pipe 67 inwhich there is interposed the electrically controlled valve 65 which, inthe rest condition, is also in the blocking posi 1 tion.

The contactor 61 is a contactor for engaging afterburning. It iscontrolled, via a functional connection 60, by means of the controllever M in such a way as to bring about engagement of afterburningassoon as the said lever has entered the AFTERBURNING sector The changeover switch 66 can occupy one or other of two positions. In itsfirstposition, which is shown in FIG. 4 and is its normal rest position,it switches on the electrically controlled valve 29. In its secondposition, it switches on the lamp 62. This switch is driven to wards itssecond position by a relay 68 which is energized as soon as theignition-detector 30 emitsa signal I indicating that ignition of thefuel has actually been obtained in the afterburning duct.

When the contactor 61 is engaged, the electrically operated valve 65 isimmediately energized in the; opening direction in such a way as tocause, in turn,

opening of the inlet valve 19. From this moment on, therefore, thedevice for supplying afterburning fuel is in operation. In addition, andas long as no ignition signal is emitted by the detector 30, theelectrically operated valve 29 is energized in the opening direction, sothat the device 26 for igniting afterburning is in operation. On theother hand, as soon as the ignition signal is emitted, the switch 66 isdriven towards its second position. The electrically operated valve 29then resumes its rest position, that is to say its blocking posi tion,so that the device 26 for igniting afterburning is brought out ofoperation.

The lamp 62 (amber lamp) constitutes a lamp for signalling the actualfunctioning of afterburning. To this end, it is connected in such a wayas to light up as soon as the afore-said signal is emitted. It thereforeindicates, as soon as it is lit, that the igniting of afterburning hasbeen successful.

The lamp 63 (red lamp) constitutes a lamp for signalling the functioningof the device for igniting afterburning, and indicates, while it is lit,that the device is in operation. For this purpose, it is associated withthe pressure-operated switch 64 which is itself controlled by theafterburning-fuel pressure prevailing downstream of the valve 29. Whilethe latter is open, the pressureoperated switch 64 closes the circuit ofthe lamp 63, which therefore remains lit. On the other hand, the lamp 63goes out as soon as the valve 29 is closed.

The known, afterburning-initiation sequence of a turbojet engine thusequipped, will now be described.

It will be assumed that, at the moment when the pilot finds it necessaryto have maximum thrust, under afterburning conditions, at his disposalas quickly as possible, the control lever M for the turbojet engine isin the THROTTLED-DOWN DRY position (a 04 As has been explained above,the pilot cannot abruptly swing this control lever into the FULL-LOADAFTERBURNING position (a a His first duty is to shift it to theFULL-LOAD DRY position (a a and to wait there until full-load dry hasactually been established and stabilized. For this purpose, he must keepunder observation certain parameters, such as N and T and it is onlywhen each of these parameters has reached a predetermined threshold (forexample, N

8,100 rpm and T 720C), that he is allowed to engage afterburning (a aand push the lever into the THROTTLED-DOWN AFTERBURNING position (04 01This move brings into operation the device for generating the parameter,8P (by opening the valve 80), and closes the contactor 61, the effectof which is to energize the electrically operated valves 65 and 29. Thedevice 18/19 for supplying afterburning fuel is thus brought intoaction. The pump 13 is then supplied with fuel, which pressurizes theentire afterburning-fuel circuit14 17 -15 16 R R R and also theignitingfuel circuit 27 29 28 26 (since the electrically operated valve29 is energized towards its open position). In parallel with all this,the amplifier 31 associated with the ignition-detector is fed.

The injection of fuel into the combustion chamber 2 by means of theigniting injector 26 gives rise to a tongue of flame which passesthrough the turbine 3 and causes ignition of the fuel escaping from themanifolds R R R in the afterburning duct 4. As long as the valve 29 isopen, the signal-lamp 63 (red lamp) remains lit under the effect of thepressure-operated switch 64.

When ignition has actually been obtained in the afterburning duct, theignition-detector 30 emits a signal which, after being amplified in theamplifier 31, simultaneously gives rise to the closure of theelectrically operated valve 29, (and therefore to the bringing of theigniting device 26 out of operation), extinction of the signal-lamp 63,and lighting-up of the signal-lamp 62 (amber lamp).

At this moment, but only at this moment, is the pilot allowed to pushthe control lever further into the AF- TERBURNING sector, as far as theFULL-LOAD AF- TERBURNING position (a (1 In the event of unsuccessfuligniting (for example if the signal-lamp 63 still remains lit after 10seconds), the pilot is obliged to bring the control lever M back intothe DRY sector in order to avoid any thermal over loading of theturbine.

The course of this known sequence is diagrammatically shown in FIG. 8 inthe form of a combination of charts.

It will be seen that this sequence is long and requires the observanceof special precautions on the part of the pilot, but does not therebyexclude all risk of incorrect operation or thermal overloading of theturbine.

A device for programming the afterburning-initiation phase according tothe invention will now be described with reference to FIGS. 6 and 7.

A first improvement relates to the utilization, under conditions whichwill be described later on, of a device for temporarily restraining theflow of afterburning fuel.

As will be seen, the temporary restraining of the flow of fuel isachieved by modifying the coefficient B with the aid of apressure-modifying reducer such as the one shown in FIG. 6. Thispressure-modifying reducer is supplied with fluid, for example air, at apressure of 3P and essentially comprises a capacity 145 (which may, ifnecessary, be identical to the capacity 45 described in connection withFIG. 5) working in conjunction with two constricted orifices 70, 71.Through the orifice 71, the capacity 145 opens on to a space which isunder low pressure (for example the atmosphere or a space which is undersubatmospheric pressure). Through the orifice 70, this capacity issupplied with fluid at the pressure ,BP In the example illustrated, themodifying pressure-reducer /145/71 is fed by the main pressure-reducer21 and thus constitutes, in the pressure-reducing device R, an auxiliarypressurereducer. The constricted orifice 71 forms a leakage path throughwhich, during operation, the fluid escapes from the capacity at a sonicspeed.

Means, such as an electrically operated valve ADF, make it possible toestablish or cut off communication between the capacity or space 145 andthe leakage path 71 so as to permit, or block, the passage of the fluidthrough the leakage path.

When the valve ADF is closed, the pressures prevailing in the twocapacities 50 and 145 are equal, because there is no flow through theconstricted orifice 70. Under these circumstances, there is set up, inthe capacity 145, a pressure 8?; which is equal to that prevailing inthe capacity 45 of the pressure-reducing device illustrated in FIG. 5.In other words, when the valve ADF is closed, the pressure-reducingdevice improved in accordance with the invention functions exactly likethe known device shown in FIG. 5.

If, on the other hand,the valve ADF is open, the fluid having a pressureof P which arrives by way of the pipe 20 undergoes two successivepressure-reducing opera tions, the first in the main pressure-reducer 21(52/50/51) and the second in the auxiliary pressurereducer 70/145/71.Under these circumstances, there is set up, in the capacity 145, areduced pressure B'P in which B is a coefficient of reduction which isvery much lower than B. The auxiliary pressure-reducer 70/145/71 thusconstitutes asimple contrivance for modifying the coefficient B, withthe aid of which the flow of afterburning fuel metered by theregulator/metering device 17 can be modified so as to change from itsnormal value C= BP fla) to a greatly reduced value C BP f (a).

With reference to FIG. 7, a description will now be given of asimplified functional diagram of an installation equipped with aprogramming device permitting the initiation of afterburning inaccordance with a sequence which is in conformity with the invention.

In this Figure, there will again be found a number of elements whichhave already been described in connection with FIG. 4, in particular theelectrically operated valve 65 for controlling the supply device 18/19for afterburning fuel, the electrically operated valve 29 forcontrolling the igniting device 26, the signal-lamp 62 for indicatingthe actual functioning of afterburning (amber lamp), the signal-lamp 63for indicating that the igniting device is functioning (red lamp), thepressure-operated switch 64, the ignition-detector 30, and the amplifier31. The auxiliary pressure reducer 70/145/71, which has already beendescribed in connection with FIG. 6 and which can be brought into, orout of, action with the aid of the electrically operated valve ADF, willalso be recognised.

This installation is supplemented as will be explained below.

The reference numeral 100 has been used to designate anafterburning-preselection device which can occupy either a positioninvolving DRY functioning or a position involving functioning underAFTERBURN- ING conditions. This preselection device is constituted by anelectrical contactor which is controlled, via a functional connection101, by meansof the engine control lever M in such a way that passagefrom the DRY position to the AFTERBURNING position occurs when thislever enters the AFTERBURNING sector (a The contactor 100 preselects thefeeding of an electrical circuit comprising, in particular, anelectronic switch 102, such as a transistor, and a change-overelectrical switch 110.

The transistor 102is biased on its base by a signal which is emitted bya threshold-type comparator 103 and amplified in an amplifier 104. Thecomparator 103 receives one or a number of signals, such as X and Y,which are emitted by one or a number of suitable pickups (notillustrated) and are compared with one or a number of reference signalsX Y The signals X, y are constituted by at least one signal which isrepresentative of a working parameter of the DRY turbojet engine, suchas the rotational speed N of the compressor, or the gas temperatures, Tor T at the entrance to, or exit from, the turbine. The referencesignals are advantageously constituted by signals which arerepresentative of a predetermined threshold (preferably the full-loadDRY value) of the abovementioned parameters, for example N 8,100 r.p.m.and T 720C. So

long as the parameter or parameters X, Y have not reached theabove-mentioned threshold, the signal emitted by the comparator 103 hasthe effect of keeping the transistor 102 in the blocked non-conductive I7 state. On the other hand, as soon as this threshold "is reached, thecomparator 103 emits a signal for the pur-.

pose of unblocking the transistor. The automatic maintenance of thetransistor 102 in the conductive state'is then effected with the aid ofa return loop 105 comprising, in particular, a diode 106. As willberealised, the purpose of this automatic maintenance is to eliminateall risk of premature stoppage of afterburning in the v I event of amomentary variation in one of the abovementioned parameters, inparticular the speed ofrotation N.

The transistor 102 thus constitutes the equivalent of a locking devicewhich prohibits the actual functioning; of afterburning until full-loadDRY hasbeen reached.

The change'over switch may occupy one or other of two positions. In itsfirst position, which is illustrated in .FIG. 7 and is its normal restposition, it switches on, via a time switch120, the electricallyopelectrically operated valve 29 is then energized in vthe direction ofopening, sothat the ignitingdevice 26 is brought intooperation- In itssecond position, the change-over switch 110 switches on, on the onehand, the signal-lamp 62 indicating the actual functioning ofafterburning (amber lamp) and, on the other hand, theelectricallyoperated valve ADF, through a timing device 130. Assumingthat the preselection device 100 and the electronic switch 7 V 102 areclosed, the lamp 62 then lights up. Concurrently, the electricallyoperated valve ADF is energized through the timing device 130, but onlyafter a prede; termined delay, for example of the order of 1.5 sec-'onds, in such a way as to bring the auxiliary pressure reducer 70/145/71out of action.

The change-over switch 110 is driven towards its second position by arelay 111 which is energized as soon as the ignition-detector 30 emits asignal indicating that 1 ignition of the fuel has actually been obtainedin the afterburning duct.

In the absence of any signal emanating from the ignition-detector 30,that is to say,.in the event of unsuccessful igniting, the time switchmakes it possible to interrupt the energization of the operated valvev29,

so as to bring the igniting device 26 out ofoperation.

The time switch 120 may be designed to open automatically at the end ofa predetermined period of time (for example eight seconds), countingfrom the start of the injection of igniting fuel (that is to say, fromthe mo-;

ment at which the transistor 102 has been unblocked).

A two-position change-over switch has been designated by the referencenumeral .140. In its first position which is its normal position,.asillustrated in FIG. "I,

and which alone will be considered below the switch enables theelectrically operated valve ADF to control, under the circumstanceswhich will be considered below, the bringing of the auxiliary pressurereducing device 70/145/71 into, or out of, action. In' its I secondposition which, in principle, is only an emergency position it connectsthe valve ADF with a source of electrical power 150, so that the valveADF is permanently energized towards its blocking position. Everythingthen takes place as if the auxiliary pressure reducing device 70/145/71were eliminated. This arrangement may be useful, particularly in theevent of a breakdown in the normal regulation of afterburning, and mayfacilitate the implementation of simplified, emergency regulation.

A description will now be given of the afterburninginitiation sequencewhich can be accomplished with the aid of the programming deviceaccording to the invention, which has just been described.

It will be assumed, as in the case of FIG. 4, that at the moment atwhich the pilot finds that he needs to have the maximum afterburningthrust at his disposal as quickly as possible, the engine control leverM is in the Tl-lROTTLED-DOWN DRY position (a 01,).

At this moment, the preselection device 100 is still in its DRYoperating position, the transistor 102 is blocked, the change-overswitch 110 is in its first position (illustrated in FIG. 7), theelectrically operated valves 65 and 29 are in the blocking position, theelectrically operated valve ADF is in the opening position (theauxiliary pressure reducing device 70/145/71 is therefore ready tooperate) and the lamps 62 and 63 are extinguished.

Without waiting, the pilot then swings his control lever directly intothe AFTERBURNING sector, as far as the FULL-LOAD AFTERBURNING position.At the moment at which this lever enters the AFTER- BURNING sector (a 01the contactor 100, which constitutes the afterburning-preselectiondevice, takes up its position for functioning under afterburningconditions. From this moment on, functioning under afterburningconditions is preselected and the sequence continues in an automaticmanner.

Because the control lever M has reached and passed the FULL-LOAD DRYposition (a the turbojet engine is, to start with, called upon toworking at fullload dry. The functioning parameter or parameters, X, Y,of the DRY engine (in particular, the rotational speed N of thecompressor, and the temperatures, T;, or T of the gases at the turbine)progressively reach the threshold X Y indicating that the DRY full loadhas actually been obtained. At this moment, the threshold-typecomparator 103 emits a signal which un- 2 blocks the transistor 102.

The electrically operated valve 65 is then energized towards its openingposition, so that the inlet valve 19 opens and brings into operation thesupply device 18/19 for afterburning fuel. The pump 13 is thus suppliedwith fuel, which pressurizes the entire afterburning-fuel circuitl4/l7/l5/l6/R /R /R and gives rise to the injection of fuel into theafterburning duct 4 through the manifolds R R R In parallel with this,the electrically operated valve 29 is energized towards its openingposition, so that the igniting fuel circuit 27/29/28/26 is pressurized.The igniting device comprising the igniting injector 26 is thereforebrought into operation, and the signal-lamp 63 (red lamp) lights up.

The injection of fuel into the combustion chamber 2 by means of theigniting injector 26 produces a tongue of flame which passes through theturbine 3 and gives rise, after a certain period of time, to igniting ofthe fuel discharging from the manifolds R R R in the afterburning duct4.

When ignition has actually been obtained in the afterburning duct, theignition-detector 30 emits a signal which, after being amplified in theamplifier 31, causes the change-over switch 110 to swing towards itssecond position. At this moment, the electrically operated switch 29ceases to be energized and returns to the blocking position, which givesrise to the bringing out of operation of the igniting device 26, and toextinction of the signal-lamp 63. At the same time, the signal lamp 62(amber lamp) lights up, indicating that igniting has been successful andthat afterburning is beginning to function in an effective manner.

In the event of unsuccessful igniting, the time switch 120 automaticallyeffects the return of the electrically operated switch 29 to itsblocking position after a predetermined period of time (for exampleeight seconds), in order to bring the igniting device 26 out ofoperation. The pilot then returns the control lever M to the DRY sector,and attempts to effect igniting again.

Consideration will now be given to the behaviour of theregulator/metering device 17 associated with the auxiliary pressurereducing device /145/71, throughout the period of afterburning-initiation.

Until the pilot has preselected functioning under afterburningconditions with the aid of the control lever M, the pressure-reducingdevice R intended to produce the reduced-pressure parameter ,BP is atrest, that is to say, is not supplied with air at a pressure of P Thecoefficient B is then equal to one, as has been seen.

As soon as the pilot has preselected functioning under afterburningconditions with the aid of the lever M, the pressure-reducing device Rbegins to function. Now, as has been seen, the electrically operatedvalve ADF is in the opening position at this moment, so that theauxiliary pressure-reducer 70/145/71, is in operation. Thepressure-reducer R then produces a reduced pressure B'P which is verymuch lower than the reduced pressure 8P required for normal metering ofthe flow of afterburning fuel, since B is a coefficient of reductionwhich is very much lower than the coefficient B. It is thus reducedpressure BP which, according to one of the essential aspects of theinvention, makes it possible to temporarily restrain the flow ofafterburning fuel when afterburning is being initiated.

The auxiliary pressure reducing device 70/145/71 may be contrived insuch a way, by suitable dimensioning of the constricted orifices 70 and71, that the restrained flow of afterburning fuel is very low, forexample equal to or lower than the flow of fuel normally correspondingto Throttled-down Afterburning and this in spite of the fact that theengine lever M is already occupying the FULL-LOAD AFTERBURING (a aposition at this moment. Everything therefore takes place during theperiod of intervention of the auxiliary pressure reducing device, as ifthe lever M were being kept in the ENGAGEMENT AFTERBURNING (a 0: orTHROTTLED-DOWN AFTERBURNING (a a,,) position. An idle period in theoperation of establishing afterburning, and an awkward restraint for thepilot are thus eliminated.

The auxiliary pressure reducing device 70/145/71 remains in action untilthe moment when ignition of the fuel has actually been obtained in theafterburning duct. At this moment, as has been seen, the changeoverswitch swings towards its second position, in

whichit switches on not only the signal-lamp 62 but also theelectrically operated valve ADF. The latter is then energized towardsits closing position, so that the auxiliary pressure reducing device70/145/71 is brought out of action. The reduced-pressure parameter thenresumes its normal value [3P and the regulation of afterburning can thenproceed under the usual conditions,

The timing device 130 makes it possible to introduce a predetermineddelay (for example of the order of 1.5 seconds) in the command forbringing the auxiliary pressure reducing device 70/145/71 out of action,after the moment at which the ignition signal has been emitted. It isthus possible to prolong the intervention of the auxiliary pressurereducing device slightly beyond the moment at which afterburning hasactually been started in the afterburning duct, so as to enable theafterburning to become stable.

The development of the initiation sequence according to the invention isshown in FIG. 9 in the form of a combination of charts.

A comparative examination of the charts illustrated in FIGS. 8 and 9clearly shows the characteristic advantage obtained by the invention.

There will more particularly be noticed the difference which existsbetween lever-control at one go (direct movement from 11 to a accordingto the invention, and lever control, by successive stages (01,, d awhich has hitherto seemed obligatory when initiating afterburning. Beingfreed from conventional duties, the pilot can in fact, by virtue of tothe invention, directly preselect FULL-LOAD AFTERBURN ING, theproduction of which only becomes effective after an automatic sequencecomprising the unlocking of the transistor 102 and the closure of theelectrically operated valve ADF.

This automatic sequence which simplifies the task of the pilot andreduces the risk of incorrect operations leads to a major saving intime. It is because of this, for example, that the maximum thrust underafterburning conditions can be obtained, thanks to the use of theprogramming device according to the invention, at the end of 8 to 10seconds, whereas the waiting time, in the case of a turbojet enginehaving conventional control, could be as much as to seconds.

Another major advantage lies in the limitation of the period offunctioning of the igniting injector 26, particularly in the event ofunsuccessful ignition, by means of the time switch 120 which in any caselimits the period,

for which igniting fuel is injected to, for example, eight seconds. Onthe other hand, in the case of a turbojet engine having conventionalcontrol, the pilot was himself obliged to keep this injection periodunder observation and bring the control lever M back into the DRYsector, for example after ten seconds. If this requirement wereoverlooked, therefore, there was a serious danger of thermal overloadingof the turbine, a risk which is particularly eliminated, owing to theinvention.

The programming device according to the invention may, if necessary, besimplified as regards the control of the locking transistor 102. Infact, the reaching of its reference threshold by only one of the abovementioned parameters X, Y may be sufficient for it to be assumed, undercertain circumstances, that the turbojet engine has virtually attainedfull-load DRY conditions. Thus, for example, it was ascertained byexperi- 116 ment that, in the case of certain turbojets engines, therotational speed N and the temperature T were reaching their full-loadDRY values in a substantially concomitant manner, with, for example, adelay of the] order of three seconds between the moment at which therotational speed N settled at its full-load DRY.

value, and that at which the temperature T, in turn reached itsfull-load DRY threshold, It is then possible,

in this event, to rely solely upon the speed signal N. for

the purpose of controlling the unlocking of the transistor 102.

It has been assumed up to now that the igniting de-.

vice was being supplied with igniting fuel emanating from theafterburning-fuel circuit. But it is clear that the igniting fuel mightalso be taken off from the main fuel circuit 8/9/l0. The igniting devicemight, moreover, comprise means other than a fuel injector, such as, forexample, an electric ignition of the spark, or incandescent filamenttypes. As regards the means, which were described in detail in the formof an inlet valve 19, for bringing into,,or out a of, operation thedevice for supplying afterburning fuel,

thismeans might comprise, either additionally or as a I variant form,means which make it possible to bring the pump 13, or a member drivingthe pump, into, or out of, operation.

It will also be noted that certain, at least, of the electrical orelectronic components of the various detection or control circuits mightbe replaced by fluidic components.

We claim:

1. In and for a turbojet engine comprising a compressor, an afterburningduct, means for supplying said afterburning duct with fuel, and meansfor metering the flow of fuel injected into said duct, saidflow-metering means being sensitive to a parameter ,BP in which P5 is acharacteristic working pressure of said compressor,

and B is a coefficient which is lower than, or at most equal to one, incombination, a device for programming the afterburning-initiation phasecomprising, means for modifying said coefficient B to temporarily reducesaid coefficient ,8 during the afterburninginitiation phase, and meansfor automatically disabling said B-modifying means after the moment atwhich ignition of the fuel has actually been obtained in theaftion-detecting device which emits a signal at the moment at whichignition of the fuel has actually been .obtained in the afterburningduct, in which saidmeans for disabling said ,B-modifying means arecontrolled by said ignition signal. 4. Aprogramming device according toclaim 3 in which a timing device is provided which is designed in such away as to introduce a predetermineddelay into the disabling of saidfl-modifying means, after the moment at which said ignition signal hasbeen emitted.

5. A programming device according to claim I in which said ,B-modifyingmeans comprise a pressure modifying reducer which is supplied with fluidat a pressure of 3P and said means for disabling the B-modifying meanscomprise means for disabling said pressure-modifying reducer.

6. A programming device according to claim 5 for application to aturbojet engine of the type in which the pressure parameter ,BP isgenerated from the pressure P in a pressurereducing device comprising atleast one main pressure-reducer, in which said pressuremodifying reducercomprises an auxiliary pressurereducer which is fed by said mainpressure-reducer.

7. A programming device according to claim 5 in which saidpressure-modifying reducer comprises a Ca pacity which is fed through aconstricted orifice with fluid at a pressure of 8P and communicates witha low pressure space through another constricted orifice forming aleakage path through which, under operating conditions, the fluidescapes from said capacity at sonic speed, and said means for disablingsaid pressuremodifying reducer comprise means for stopping the escape ofthe fluid through said leakage path.

8. A programming device according to claim 7 in which said means fordisabling the pressure-modifying reducer comprise means for cutting offthe communication between said capacity and said leakage path.

9. A programming device according to claim 1 and comprising, inaddition, means for activating or deactivating said device for supplyingafterburning fuel; an afterburning-preselection device, which may occupyeither a DRY functioning position or else a position for functioningunder afterburning conditions; and means sensitive to at least oneworking parameter of the DRy turbojet engine; said means being designedto automatically activate said supplying device when, with saidpreselection device in the position for functioning under afterburningconditions, such parameter reaches a predetermined threshold.

10. A programming device according to claim 9 for application to aturbojet engine equipped with a device for igniting the fuel discharginginto the afterburning duct, which igniting device can be activated ordeactivated; in which said means sensitive to such functioning parameterof the turbojet are also adapted to automatically activate said ignitingdevice when, with said preselection device in the position forfunctioning under afterburning conditions, such parameter reaches saidthreshold.

11. A programming device according to claim 10, and comprising, inaddition, timing means designed to automatically deactivate saidigniting device after a predetermined period of time, starting from themoment at which said igniting device has been activated.

12. A programming device according to claim 10 for application to aturbojet engine equipped with an ignition-detecting device which emits asignal at the moment at which ignition of the fuel has actually beenobtained in the afterburning duct, in which means are provided which arecontrolled by said ignition signal and are designed to automaticallydeactivate said igniting device.

13. A programming device according to claim 9 in which said meanssensitive to such working parameter of the DRY turbojet engine comprisea locking device which is kept in the locked position until suchparameter reaches said threshold.

14. A programming device according to claim 9 in which such workingparameter comprises the rotational speed of the compressor of theturbojet engine.

15. A programming device according to claim 9 in which such workingparameter comprises the temperature prevailing immediately downstream ofthe expansion turbine.

16. A programming device according to claim 9 for application to aturbojet engine equipped with a lever for controlling the afterburningload, in which said afterburning-preselection device is coupled to saidcontrol lever.

1. In and for a turbojet engine comprising a compressor, an afterburningduct, means for supplying said afterburning duct with fuel, and meansfor metering the flow of fuel injected into said duct, saidflow-metering means being sensitive to a parameter Beta P2, in which P2is a characteristic working pressure of said compressor, and Beta is acoefficient which is lower than, or at most equal to one, incombination, a device for programming the afterburning-initiation phasecomprising, means for modifying said coefficient Beta to temporarilyreduce said coefficient Beta during the afterburning-initiation phase,and means for automatically disabling said Beta -modifying means afterthe moment at which ignition of the fuel has actually been obtained inthe afterburning duct.
 2. A programming device according to claim 1 forapplication to a turbojet engine equipped with a lever for controllingthe afterburning load, in which said Beta -modifying means are designedto reduce the flow of afterburning fuel to a value which is close to theThrottled-down afterburning flow, whatever the position of said controllever.
 3. A programming device according to claim 1 for application to aturbojet engine equipped with an ignition-detecting device which emits asignal at the moment at which ignition of the fuel has actually beenobtained in the afterburning duct, in which said means for disablingsaid Beta -modifying means are controlled by said ignition signal.
 4. Aprogramming device according to claim 3 in which a timing device isprovided which is designed in such a way as to introduce a predetermineddelay into the disabling of said Beta -modifying means, after the momentat which said ignition signal has been emitted.
 5. A programming deviceaccording to claim 1 in which said Beta -modifying means comprise apressure-modifying reducer which is supplied with fluid at a pressure ofBeta P2, and said means for disabling the Beta -modifying means comprisemeans for disabling said pressure-modifying reducer.
 6. A programmingdevice according to claim 5 for application to a turbojet engine of thetype in which the pressure parameter Beta P2 is generated from thepressure P2 in a pressure-reducing device comprising at least one mainpressure-reducer, in which said pressure-modifying reducer comprises anauxiliary pressure-reducer which is fed by said main pressure-reducer.7. A programming device according to claim 5 in which saidpressure-modifying reducer comprises a capacity which is fed through aconstricted orifice with fluid at a pressure of Beta P2, andcommunicates with a low pressure space through another constrictedorifice forming a leakage path through which, under operatingconditions, the fluid escapes from said capacity at sonic speed, andsaid means for disabling said pressure-modifying reducer comprise meansfor stopping the escape of the fluid through said leakage path.
 8. Aprogramming device according to claim 7 in which said means fordisabling the pressure-modifying reducer comprise means for cutting offthe communication between said capacity and said leakage path.
 9. Aprogramming device according to claim 1 and comprising, in addition,means for activating or deactivating said device for supplyingafterburning fuel; an afterburning-preselectiOn device, which may occupyeither a DRY functioning position or else a position for functioningunder afterburning conditions; and means sensitive to at least oneworking parameter of the DRy turbojet engine; said means being designedto automatically activate said supplying device when, with saidpreselection device in the position for functioning under afterburningconditions, such parameter reaches a predetermined threshold.
 10. Aprogramming device according to claim 9 for application to a turbojetengine equipped with a device for igniting the fuel discharging into theafterburning duct, which igniting device can be activated ordeactivated; in which said means sensitive to such functioning parameterof the turbojet are also adapted to automatically activate said ignitingdevice when, with said preselection device in the position forfunctioning under afterburning conditions, such parameter reaches saidthreshold.
 11. A programming device according to claim 10, andcomprising, in addition, timing means designed to automaticallydeactivate said igniting device after a predetermined period of time,starting from the moment at which said igniting device has beenactivated.
 12. A programming device according to claim 10 forapplication to a turbojet engine equipped with an ignition-detectingdevice which emits a signal at the moment at which ignition of the fuelhas actually been obtained in the afterburning duct, in which means areprovided which are controlled by said ignition signal and are designedto automatically deactivate said igniting device.
 13. A programmingdevice according to claim 9 in which said means sensitive to suchworking parameter of the DRY turbojet engine comprise a locking devicewhich is kept in the locked position until such parameter reaches saidthreshold.
 14. A programming device according to claim 9 in which suchworking parameter comprises the rotational speed of the compressor ofthe turbojet engine.
 15. A programming device according to claim 9 inwhich such working parameter comprises the temperature prevailingimmediately downstream of the expansion turbine.
 16. A programmingdevice according to claim 9 for application to a turbojet engineequipped with a lever for controlling the afterburning load, in whichsaid afterburning-preselection device is coupled to said control lever.